In a rare interview, the Syrian President told the AFP news agency that he realised that the involvement of regional and international forces “means that the solution will take a long time and will incur a heavy price”.

He styled his opponents as “terrorists”, although Syrian forces have mainly been fighting anti-government rebels including theFree Syrian Army, who were initially supported and trained by the US.

Isis holds swathes of the country, as does a coalition of other Islamist groups including the al-Qaeda-affiliated Jabhat al-Nusra.

He was speaking shortly before diplomats at the current Syria peace talks in Munich agreed a temporary “cessation of hostilities” in Syria’s civil war within a week, although efforts to secure a lasting ceasefire fell short.

The deal appeared to be the result of a compromise between the US, which had wanted an immediate stop to fighting, and Russia, which had proposed one to start on March 1.

Syrian civilians among the rubble in rebel-held Aleppo after Russian-backed air strikes

“The real test is whether or not all the parties honour those commitments and implement them,” John Kerry, the US Secretary of State, said in the early hours of Friday.

Discussions between the Syrian regime and anti-government rebels are due to re-start on 25 February after breaking down rapidly last month as Assad’s military made significant advances backed by Russian air strikes.

In recent weeks, government forces have closed in on Aleppo, Syria’s largest city, and are now targeting the Free Syrian Army’s last remaining supply line.

Assad’s troops are also closing in on the north-eastern city of Idlib, which is held by Jaysh al-Fatah (Army of Conquest), the Islamist coalition including the al-Qaeda linked Jabhat al-Nusra, Ahrar ash-Sham and Jund al-Aqsa.

Civilians react following a reported Syrian regime air strike in a rebel-controlled area in Aleppo

They are internationally recognised as terrorist groups and have not been invited to peace talks, but the US-led alliance have been at loggerheads with Syria, Russia and Iran over the inclusion of other rebels.

Russia’s air strikes, which started in September at Assad’s request, have been accused of “indiscriminately” targeting residential areas held by “moderate” rebels and killing countless civilians, while the US-led coalition’s bombing has concentrated on Isis territory.

The West considers Assad’s resignation as the key and perhaps only way to stop the Syrian war but he has doggedly refused to go.

David Cameron has repeatedly said the Syrian President has no place in the country’s future and has called for peaceful transition to a new government, in line with Barack Obama, Francois Hollande and other leaders in the US-led international coal

Saudi Arabia’s foreign minister reinforced the sentiment today, saying his country’s objective was to remove Assad, which he considers a necessary step to defeat Isis and end the conflict.